Corrosion Of Steel In Acid Medium Research Articles

The inhibition of mild steel corrosion in acidic medium by 2,2′-bis(benzimidazole)

A new corrosion inhibitor, namely 2,2′-bis(benzimidazole) has been synthesised and its inhibiting action on the corrosion of mild steel in acidic bath (1 M HCl) has been investigated by various corrosion monitoring techniques, such as corrosion weight loss test and potentiodynamic polarisation. The results of the investigation show that this compounds have fairly good inhibiting properties for steel corrosion in hydrochloric acid, and is a mixed inhibitor in (1 M HCl). The adsorption of this inhibitor is also found to obey the Langmuir adsorption isotherm.

Experimental and theoretical study of 1-(2-ethylamino)-2-methylimidazoline as an inhibitor of carbon steel corrosion in acid media

The electrochemical behavior of 1-(2-ethylamino)-2-methylimidazoline (imidazoline), its precursor N-[3-(2-amino-ethylamino-ethyl)]-acetamide (amide) and its derivative 1-(2-ethylamino)-2-methylimidazolidine (imidazolidine), is evaluated by using potentiodynamic polarization curves and electrochemical impedance spectroscopy, EIS, techniques in deaerated acid media to compare their corrosion inhibition efficiency. The experimental results suggest that imidazoline is a good corrosion inhibitor at different concentrations whereas amide shows low efficiency values; however, the properties of a corrosion inhibitor were not found in imidazolidine. The reactivity of these compounds was analyzed through theoretical calculations based on density functional theory (DFT) to explain the different efficiencies of these compounds as corrosion inhibitors both in the neutral and protonated form. The theoretical results indicate that imidazoline is the more efficient corrosion inhibitor because of its two very active sites (two nitrogen atoms) and the plane geometry of the heterocyclic ring, thus promoting coordination with the metal surface.

AC and DC study of the temperature effect on mild steel corrosion in acid media in the presence of benzimidazole derivatives

The effect of benzimidazole derivatives on mild steel corrosion in 1 M HCl at five different temperatures has been studied. Impedance, polarization resistance, polarization curves measurement and gravimetric methods have been used. The inhibiting efficiency and the apparent activation energy ( E a) have been calculated in the presence and in the absence of the organic inhibitors. The comparative investigations carried out in 1 M H 2SO 4 and 1 M H 2SO 4+1×10 −4 M KI verify the assumption that the halogen ions facilitate the inhibitors adsorption. The electrostatic absorption of the compound cation form seems more probable. The behaviour of 2-mercaptobenzimidazole (2-SH-BI) contrasts that of the rest of the substances investigated. Chemisorptive adsorption is more probable in this case. The lower value of activation energy E a in the presence of 1-benzyl-benzimidazole when compared to that in 1 M HCl is explained with a partial compensation effect.

Study of the mechanism and inhibiting efficiency of 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole on mild steel corrosion in acidic media

The efficiency of a new triazole derivative, namely, 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) has been studied for corrosion inhibition of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulphuric acid (H 2SO 4). Corrosion inhibition was studied using electrochemical methods and weight loss measurements. These studies have shown that 4-MTHT was a very good inhibitor. 4-MTHT behaved better in 1 M HCl than in 0.5 M H 2SO 4 and inhibition efficiencies up to 99% and 80% can be obtained in 1 M HCl and 0.5 M H 2SO 4, respectively. Activation energies ( E a) in the presence and absence of 4-MTHT were obtained by measuring the temperature independence of the corrosion current. The potential of zero charge of mild steel was studied by ac impedance method, and the mechanism of adsorption has been discussed. The adsorption of 4-MTHT followed Langmuir's adsorption isotherm in both acids.

Frequency Dispersion of the Interfacial Impedance at Mild Steel Corrosion in Acid Media in the Presence of Benzimidazole Derivatives

Measurements of the complex impedance of the interface between mild steel and deaerated 1 M HCl solutions without and with the addition of different inhibitors, derivatives of benzimidazole, have been made in the frequency range of (0.1−9.5) × 104 Hz. Adequate structure models of the interfaces as well as some data on the kinetics of the partial processes are offered. It is found that the double-layer capacity as well as the adsorption capacity can not be presented by a frequency independent lumped element. The experimental data show a frequency distribution and therefore a modeling element with frequency dispersion behavior; a constant phase element has been used. At high inhibitor concentrations a second time constant is clearly observed in the impedance spectra. It is most probably connected with the adsorption process. Two time constants determined by the charge transfer and the adsorption of the inhibitor, respectively, can be readily outlined.